Question

What is ∑n=16[4(−5)n−1] equal to?

Enter your answer in the box.

Answer 1

Explanation:

Geometric Sequence formula for general term:

an = a1(r^n-1)

a1 = 4 × (-5)^1-1

a1 = 4

r = -5

Summation formula for geometric sequence :

Sn = a1 ( 1 - r^n / 1 - r )

...take n from the top of the summation.

= 4 ( 1 -(-5)^6 / 1 -(-5)

= -10416.